Method of composite gate formation

ABSTRACT

Methods for forming a nitride barrier film layer in semiconductor devices such as gate structures, and barrier layers, semiconductor devices and gate electrodes are provided. The nitride layer is particularly useful as a barrier to boron diffusion into an oxide film. The nitride barrier layer is formed by selectively depositing silicon onto an oxide substrate as a thin layer, and then thermally annealing the silicon layer in a nitrogen-containing species or exposing the silicon to a plasma source of nitrogen to nitridize the silicon layer.

FIELD OF THE INVENTION

[0001] The present invention relates generally to semiconductorfabrication and, more particularly, to methods of forming nitridebarrier layers used in semiconductor devices.

BACKGROUND OF THE INVENTION

[0002] Metal-insulator-silicon (MIS) transistors, includingmetal-oxide-silicon (MOS) transistors, are comprised of doped source anddrain regions formed in the surface of a semiconductor substrate, achannel region between the source and drain, and a gate electrodesituated over the channel region. The gate electrode is physically andelectrically separated from the channel by a thin gate dielectric(oxide) layer, typically silicon dioxide. The gate electrode typicallycomprises a doped polysilicon material. Diffusion of dopants such asboron from the doped polysilicon gate through the gate oxide layer intothe underlying silicon substrate poses serious problems in processingand the functioning of the device.

[0003] To inhibit boron diffusion, nitrogen has been incorporated intothe gate oxide layer. One conventional method of incorporating nitrogeninto the oxide layer is by anneal of the oxide layer in nitric oxide(NO), nitrous oxide (N₂O), ammonia (NH₃) or other nitrogen-containingspecies. However, thermal nitridation of the gate oxide layer results innitrogen incorporation at the silicon/oxide interface, which increasesthe ability of the gate oxide layer to suppress boron penetration butcan result in transconductance loss.

[0004] Another method of forming a nitrided gate oxide layer is byremote plasma nitridation by exposing the surface of the oxide layer toa plasma generated species of nitrogen. This results in thepolysilicon/oxide interface being nitridized as opposed to the gateoxide/silicon interface, thus avoiding transconductance loss. However,data indicates that the plasma nitridation may not be scaleable below 25angstroms for integrated circuit (IC) devices with high processingthermal budgets such as DRAMS or flash devices due to the loss ofintegrity of the gate oxide as well as the loss of transconductance dueto the proximity of nitrogen to the gate oxide-silicon interface.

[0005] Another conventional method to incorporate nitrogen into the gateoxide layer is to form a composite gate dielectric layer comprising asilicon nitride layer and an oxide layer. An issue with forming such acomposite gate oxide is that the interface between the silicon nitrideand oxide layers typically requires rigorous post-treatment processingto eliminate potential sources of charge trapping. In addition,composite gate dielectrics that comprise nitride and thermal oxides havelimitations due to the total effective oxide thickness that can beachieved due to poor nucleation of nitride on oxide. This requires theformation of a relatively thick nitride layer resulting in an overalleffective oxide thickness that is higher than that which is consideredas usable.

[0006] Thus, a need exists for a nitride barrier layer that avoids suchproblems.

SUMMARY OF THE INVENTION

[0007] The present invention provides methods for forming a nitridebarrier film layer useful in fabrication of semiconductor devices suchas gate structures. The nitride layer is particularly useful as abarrier to boron diffusion into an oxide film.

[0008] In one aspect, the invention provides methods for forming anitride barrier layer over a dielectric (oxide) substrate. Thedielectric layer is exposing to a silicon-containing species under lowpartial pressure, high vacuum to nucleate the surface of the dielectriclayer and deposit a thin layer of silicon, which is then exposed to anitrogen-containing species to nitridize the silicon and form a siliconnitride barrier layer. The silicon-containing species can be deposited,for example, by plasma enhanced chemical vapor deposition, low pressurechemical vapor deposition, rapid thermal chemical vapor deposition,among other processes. The silicon layer can comprise polysilicon oramorphous silicon. In an embodiment of the method, an oxide layer isirradiated with a silicon-containing species at a low partial pressureof about 10⁻² Torr (10 mTorr) or less to selectively deposit a thinlayer of silicon onto the oxide surface, preferably about 10 to about 20angstroms thick. The silicon layer can then be thermally annealed in anitrogen-containing species at a preferred temperature of about 700° C.to about 900° C., or exposed to a plasma source of nitrogen to nitridizethe silicon. The plasma nitrogen can be produced, for example, by adownstream microwave system, an electron cyclotron residence system, aninductive coupled plasma system, a radio frequency (RF) system, amongothers.

[0009] In another aspect, the invention provides methods for forming asemiconductor device. In one embodiment, the method comprises exposing adielectric layer disposed on a silicon substrate to a silicon-containingspecies under a low partial pressure of about 10⁻² Torr or less, and aflow rate of less than 100 sccm to deposit a layer of about 10 to about20 angstroms silicon; and exposing the silicon layer to anitrogen-containing species to nitridize the silicon and form a siliconnitride barrier layer. The silicon layer can be thermally annealed in anitrogen-containing species, preferably at a temperature of about 700°C. to about 900° C., or exposed to a plasma source of anitrogen-containing species.

[0010] In another aspect, the invention provides methods for forming agate electrode. In one embodiment, the method comprises exposing a gateoxide (dielectric) layer disposed on a silicon substrate to asilicon-containing species at a low partial pressure of about 10⁻² Torror less to deposit a layer of about 10 to about 20 angstroms silicon;and exposing the silicon layer to a nitrogen-containing species to forma silicon nitride barrier layer. In one embodiment, the silicon layercan be thermally annealed in a nitrogen-containing species, preferablyat a temperature of about 700° C. to about 900° C. In anotherembodiment, the silicon layer can be exposed to a plasma source ofnitrogen. The method can further comprise forming a conductivepolysilicon layer comprising a boron dopant over the nitride barrierlayer, and additional layers as desired including, for example, a metalsilicide layer such as tungsten silicide (WSi_(X)), a barrier layer suchas titanium nitride (TiN), a conductive metal layer such as tungsten(W), and an insulative nitride cap. The nitride barrier layer inhibitspassage of boron from the conductive polysilicon layer into the gateoxide layer.

[0011] In another aspect, the invention provides a nitride barrierlayer. The barrier layer comprises a nitridized silicon layer of about10 to about 20 angstroms formed on an oxide layer by irradiating theoxide layer with a silicon-containing species under a low partialpressure of about 10⁻² Torr or less, and nitridizing the silicon layerto silicon nitride by exposure to a nitrogen-containing species. In oneembodiment, the nitride barrier layer comprises thermally annealednitridized silicon having a thickness of about 10 to about 20 angstroms,and disposed adjacent an oxide layer. In another embodiment, the nitridebarrier layer comprises a plasma nitrogen annealed silicon layer.

[0012] In yet another aspect, the invention provides a semiconductordevice. The device comprises a semiconductor substrate comprisingsilicon, an oxide layer disposed adjacent to the semiconductorsubstrate, and a diffusion barrier layer of about 10 to about 20angstroms disposed adjacent the oxide layer and comprising a nitridizedsilicon layer formed by irradiating an oxide layer with asilicon-containing species under low partial pressure of about 10⁻² Torror less, and nitridizing the silicon to silicon nitride by exposure to anitrogen-containing species. In one embodiment, the semiconductor devicecomprises a diffusion barrier layer comprising a thin layer of nitrogenannealed silicon, the silicon being thermally annealed or plasmaannealed in a nitrogen-containing species.

[0013] In a further aspect, the invention provides a gate electrode. Thegate electrode comprises a gate oxide layer disposed adjacent to asemiconductor substrate, typically silicon, and a diffusion barrierlayer disposed adjacent the gate oxide layer; the diffusion barrierlayer having a thickness of about 10 to about 20 angstroms andcomprising a nitridized silicon layer formed by irradiating the gateoxide layer with a silicon-containing species under low partial pressure(about 10⁻² Torr or less), and nitridizing the silicon to siliconnitride by exposure to a nitrogen-containing species. In one embodiment,the diffusion barrier layer of the gate electrode comprises siliconthermally annealed in a nitrogen-containing species. In anotherembodiment, the gate electrode comprises a diffusion barrier comprisinga plasma nitrogen annealed silicon.

[0014] The invention advantageously provides an improved interfacebetween a silicon nitride barrier layer and an underlying dielectric(oxide) layer, having less traps and requiring less post treatment(e.g., oxidation) of the gate dielectric. In addition, the inventionachieves a relatively thin nitride layer thus decreasing the effectiveoxide thickness as compared to conventionally used methods.

BRIEF DESCRIPTION OF THE DRAWINGS

[0015] Preferred embodiments of the invention are described below withreference to the following accompanying drawings, which are forillustrative purposes only. Throughout the following views, thereference numerals will be used in the drawings, and the same referencenumerals will be used throughout the several views and in thedescription to indicate same or like parts.

[0016]FIG. 1 is a diagrammatic cross-sectional view of a semiconductorwafer fragment at a preliminary step of a processing sequence.

[0017] FIGS. 2-4 are views of the wafer fragment of FIG. 1 at subsequentand sequential processing steps, showing fabrication of a nitridebarrier layer in a stacked gate electrode according to an embodiment ofthe method of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0018] The invention will be described generally with reference to thedrawings for the purpose of illustrating the present preferredembodiments only and not for purposes of limiting the same. The figuresillustrate processing steps for use in the fabrication of semiconductordevices in accordance with the present invention. It should be readilyapparent that the processing steps are only a portion of the entirefabrication process.

[0019] In the current application, the terms “semiconductive waferfragment” or “wafer fragment” or “wafer” will be understood to mean anyconstruction comprising semiconductor material, including but notlimited to bulk semiconductive materials such as a semiconductor wafer(either alone or in assemblies comprising other materials thereon), andsemiconductive material layers (either alone or in assemblies comprisingother materials). The term “substrate” refers to any supportingstructure including, but not limited to, the semiconductive waferfragments or wafers described above.

[0020] An embodiment of a method of the present invention is describedwith reference to FIGS. 1-4, in a method of forming a gate electrode ina stacked configuration. The gate electrode generally comprises a stackof materials including a gate oxide (dielectric), a conductively dopedpolysilicon, and can further include a metal silicide layer, a barrierlayer, a conductive layer, and an insulative cap.

[0021] While the concepts of the invention are conducive to thefabrication of gate electrodes, the concepts described herein can beapplied to other semiconductor devices that would likewise benefit fromthe fabrication of a nitride barrier film as described herein.Therefore, the depiction of the invention in reference to themanufacture of a stacked gate configuration is not meant to limit theextent to which one skilled in the art might apply the concepts taughtherein.

[0022] Referring to FIG. 1, a portion of a semiconductor wafer 10 isshown at a preliminary processing step. The wafer fragment 10 inprogress can comprise a semiconductor wafer substrate or the wafer alongwith various process layers formed thereon, including one or moresemiconductor layers or other formations, and active or operableportions of semiconductor devices.

[0023] The wafer fragment 10 is shown as comprising a semiconductorsubstrate 12, an exemplary substrate being a bulk substrate material ofsemiconductive or semiconductor material, for example, monocrystallinesilicon. The substrate 12 is provided with isolation regions 14 formedtherein, for example, shallow trench isolation regions. A gate oxide(dielectric) layer 16 overlies the substrate 12. The gate oxide layer 16can comprise, for example, silicon dioxide (SiO₂), tantalum pentoxide(Ta₂O₅), hafnium dioxide (HfO₂), and aluminum trioxide (Al₂O₃), amongothers. The gate oxide layer 16 can be formed by conventional methods,and is typically an oxide layer grown directly on the base siliconsubstrate material 12, but can also be a deposited layer.

[0024] According to the invention, the gate oxide layer 14 is irradiatedwith a silicon-containing species under low partial pressure, highvacuum conditions to deposit (nucleate) a thin layer 18 of silicon ontothe surface 16 of the gate oxide layer 14, as shown in FIG. 2. Thesilicon layer can comprise polysilicon or amorphous silicon. Theprocessing conditions results in a silicon layer 18 that is thinner thancan be achieved under standard silicon growth conditions, i.e., atemperature greater than 600° C., and a pressure greater than 100 mTorr,with SiH₂, Si₂H₇, or dichlorosilane (DCS, SiH₂Cl₂). Preferably, thesilicon layer 18 is less than about 30 angstroms, preferably about 10 toabout 20 angstroms thick. Exemplary silicon source materials includeSiH₂Cl₂, silicon tetrachloride (SiCl₄), and a silicon that contains ahydride such as silane (SiH₄), and disilane (Si₂H₆). The siliconmaterial can be deposited as a layer utilizing any known depositionprocess including plasma enhanced chemical vapor deposition (PECVD), lowpressure chemical vapor deposition (LPCVD), and rapid thermal chemicalvapor deposition (RTCVD).

[0025] Preferably, the silicon material is deposited using a thermaldeposition process. Processing conditions include a low partial pressureof about 10⁻² Torr or less, preferably about 10⁻² to about 10⁻⁷ Torr,preferably about 10⁻³ to about 10⁻⁵ Torr, a temperature of about 500° C.to about 700° C., with a flow rate of the silicon-containing species ofless than 100 sccm, preferably about 1 sccm to about 50 sccm, for aduration of about 1 second to about 5 minutes.

[0026] Referring to FIG. 3, the silicon layer 18 is then nitridized toconvert the silicon to silicon nitride (SiN_(X)) 20 by exposure to anitrogen-containing gas using conventional methods. Such conventionalmethods include a rapid thermal nitridization (RTN), and plasmanitridization, among others. Examples of nitrogen-containing gases foruse in such methods include nitrogen (N₂), ammonia (NH₃), nitrogentrifluoride (NF₃), nitrogen oxides (NO_(X)), and an N₂/He mixture inplasma. The use of a plasma source of nitrogen-containing gas ispreferred.

[0027] The nitridation of the silicon layer 18 takes place underconditions that are optimal for nitridation of silicon. An example andpreferred rapid thermal nitridization includes exposing the siliconlayer to ammonia (NH₃) or other nitrogen-containing ambient at atemperature of about 700° C. to about 900° C., a pressure of about 1 toabout 760 Torr, with a flow rate of about 1100 sccm to about 10,000sccm, for a duration of about 1 second to about 180 minutes. The partialpressure of the nitrogen-containing ambient can range from a low partialpressure, for example, of about 1 to about 10 Torr, up to fullatmospheric pressure to optimize processing as desired.

[0028] In a plasma nitridization of the silicon layer 18, the plasmastream can be produced by a variety of plasma sources, such as adownstream microwave system, an electron cyclotron residence (ECR)system, an inductive coupled plasma (ICP) system, a radio frequency (RF)system, among others. Exemplary plasma nitridization processes compriseexposing the wafer 10 to a remote microwave plasma source of nitrogen oran inductive coupled plasma (ICP) at a pressure of about 1 to about 20Torr. The plasma typically comprises the nitrogen-containing gas,preferably nitrogen (N₂) or ammonia (NH₃), and an inert gas such ashelium or argon to increase the plasma density.

[0029] The resulting nitride layer 20 functions as a barrier to inhibitthe passage of boron through the gate dielectric layer from an overlyingboron-doped gate polysilicon layer into the substrate 12.

[0030] The structure can then be processed by conventional methods tocomplete the gate electrode. An example of a gate stack comprises a gateoxide layer 16, a doped polysilicon layer 22, a barrier layer 24 such astungsten nitride (WN), a layer 26 of tungsten or other conductive metal,and a nitride cap 28, as shown in FIG. 4. Another example of a gatestack (not shown) comprises a gate oxide, a doped polysilicon, tungstensilicide (WSi_(X)), titanium silicide (TiSi_(X)), cobalt silicide(CoSi_(X)), and a nitride cap. The gate layers can then be patterned andetched utilizing photolithographic processing (i.e., by dry etching) toform a transistor gate stack 30, as shown. Sidewalls 32 are providedadjacent the transistor gate, and can comprise, for example, silicondioxide or silicon nitride.

[0031] Thereafter, a dopant implantation, typically with an n-typeconductivity-enhancing dopant, can be performed to form the source/drain(S/D) regions 34 in the silicon substrate 12 proximate the gate 30. Thesource/drain regions together with the gate form an operative fieldeffect transistor device.

[0032] In compliance with the statute, the invention has been describedin language more or less specific as to structural and methodicalfeatures. It is to be understood, however, that the invention is notlimited to the specific features shown and described, since the meansherein disclosed comprise preferred forms of putting the invention intoeffect. The invention is, therefore, claimed in any of its forms ormodifications within the proper scope of the appended claimsappropriately interpreted in accordance with the doctrine ofequivalents.

What is claimed is:
 1. A method of forming a nitride barrier layer,comprising the steps of: exposing a dielectric layer to asilicon-containing species under low partial pressure to deposit a layerof silicon thereon; and exposing the silicon layer to anitrogen-containing species to form a silicon nitride barrier layer. 2.The method of claim 1, wherein the dielectric layer is exposed to thesilicon-containing species at a partial pressure of about 10⁻² Torr orless.
 3. The method of claim 1, wherein the dielectric layer is exposedto the silicon-containing species at pressure of about 10⁻² to about10⁻⁷ Torr.
 4. The method of claim 2, wherein the dielectric layer isexposed to the silicon-containing species at a temperature of about 500°C. to about 700° C.
 5. A method of forming a nitride barrier layer,comprising the steps of: irradiating a dielectric layer with asilicon-containing species under low partial pressure to nucleate thedielectric layer with a layer of silicon; and exposing the silicon layerto a nitrogen-containing species to form a silicon nitride barrierlayer.
 6. The method of claim 5, wherein the silicon layer has athickness of about 10 to about 30 angstroms.
 7. A method of forming anitride barrier layer, comprising the steps of: exposing a dielectriclayer to a silicon-containing species under low partial pressure todeposit a layer of about 10 to about 30 angstroms silicon thereon; andnitridizing the silicon layer in a nitrogen-containing species to form asilicon nitride barrier layer.
 8. A method of forming a nitride barrierlayer, comprising the steps of: exposing a surface of a dielectric layerto a silicon-containing species at a low partial pressure to nucleatethe surface of the dielectric layer with a layer of silicon; andexposing the silicon layer to a nitrogen-containing species to form asilicon nitride barrier layer.
 9. A method of forming a nitride barrierlayer, comprising the steps of: exposing a dielectric layer to asilicon-containing species at a partial pressure of about 10⁻² Torr orless to deposit a layer of about 10 to about 30 angstroms siliconthereon; and nitridizing the silicon layer to form a silicon nitridebarrier layer.
 10. The method of claim 9, wherein the dielectric layeris exposed to the silicon-containing species at a temperature of about500° C. to about 700° C.
 11. The method of claim 9, wherein thesilicon-containing species is selected from the group consisting ofdichlorosilane, silicon tetrachloride, silane, and disilane.
 12. Themethod of claim 9, wherein the step of exposing the dielectric layer tothe silicon-containing species is by plasma enhanced chemical vapordeposition, low pressure chemical vapor deposition, or rapid thermalchemical vapor deposition.
 13. The method of claim 9, wherein thesilicon-containing species is deposited by rapid thermal chemical vapordeposition at about 500° C. to about 700° C.
 14. The method of claim 9,wherein the dielectric layer comprises silicon dioxide.
 15. The methodof claim 9, wherein the dielectric layer comprises a dielectric materialselected from the group consisting of tantalum pentoxide, hafniumdioxide, and aluminum trioxide.
 16. A method of forming a nitridebarrier layer, comprising the steps of: exposing a dielectric layer to asilicon-containing species at a partial pressure of about 10⁻² to about10⁻⁷ to nucleate the dielectric layer with a layer of silicon; andexposing the silicon layer to a nitrogen-containing species to form asilicon nitride barrier layer.
 17. A method of forming a nitride barrierlayer, comprising the steps of: exposing a dielectric layer to asilicon-containing species at a partial pressure of about 10⁻² to about10⁻⁷, a temperature of about 500° C. to about 700° C., and a duration ofabout 1 second to about 5 minutes, to nucleate the dielectric layer witha layer of silicon; and exposing the silicon layer to anitrogen-containing species to form a silicon nitride barrier layer. 18.A method of forming a nitride barrier layer, comprising the steps of:depositing a silicon layer onto a dielectric layer by exposing thedielectric layer to a silicon-containing species under low partialpressure; and thermally annealing the silicon layer in anitrogen-containing species.
 19. A method of forming a nitride barrierlayer, comprising the steps of: depositing a silicon layer onto adielectric layer by exposing the dielectric layer to asilicon-containing species under low partial pressure; and exposing thesilicon layer to a nitrogen-containing species at a temperature of about700° C. to about 900° C. to nitridize the silicon layer.
 20. A method offorming a nitride barrier layer, comprising the steps of: depositing asilicon layer onto a dielectric layer by exposing the dielectric layerto a silicon-containing species under low partial pressure; and exposingthe silicon layer to a nitrogen-containing species at a temperature ofabout 700° C. to about 900° C., a pressure of about 1 to about 760 Torr,and a flow rate of about 100 to about 10,000 sccm, for about 1 second toabout 180 minutes to nitridize the silicon layer.
 21. The method ofclaim 20, wherein the nitrogen-containing species is selected from thegroup consisting of nitrogen, ammonia, nitrogen trifluoride, nitrogenoxide, and a nitrogenhelium mixture.
 22. The method of claim 21, whereinthe silicon layer is exposed to a plasma source of nitrogen.
 23. Amethod of forming a nitride barrier layer, comprising the steps of:depositing a silicon layer onto a dielectric layer by exposing thedielectric layer to a silicon-containing species under low partialpressure; and exposing the silicon layer to a plasma source of anitrogen-containing species to nitridize the silicon layer.
 24. Themethod of claim 23, wherein the plasma source of the nitrogen-containingspecies is produced by a downstream microwave system, an electroncyclotron residence system, an inductive coupled plasma system, or aradio frequency system.
 25. A method of forming a nitride barrier layer,comprising the steps of: depositing a silicon layer onto a dielectriclayer by exposing the dielectric layer to a silicon-containing speciesunder low partial pressure; and exposing the silicon layer to a remotemicrowave plasma source of a nitrogen-containing species at a pressureof about 1 to about 20 Torr to nitridize the silicon layer.
 26. A methodof forming a nitride barrier layer, comprising the steps of: depositinga silicon layer onto a dielectric layer by exposing the dielectric layerto a silicon-containing species under low partial pressure; and exposingthe silicon layer to a remote microwave plasma source of anitrogen-containing species at a pressure of about 1 to about 20 Torr,and a temperature of about 700° C. to about 900° C. to nitridize thesilicon layer.
 27. A method of forming a nitride barrier layer,comprising the steps of: depositing a silicon layer onto a dielectriclayer by exposing the dielectric layer to a silicon-containing speciesunder low partial pressure; and exposing the silicon layer to aninductive coupled plasma source of a nitrogen-containing species at apressure of about 1 to about 20 Torr to nitridize the silicon layer. 28.A method of forming a semiconductor device, comprising the steps of:irradiating a dielectric layer disposed on a silicon substrate with asilicon-containing species under low partial pressure to nucleate thedielectric layer with a layer of silicon; and nitridizing the siliconlayer.
 29. The method of claim 28, wherein the step of irradiating thedielectric layer with the silicon-containing species is at a partialpressure about 10⁻² Torr or less.
 30. The method of claim 29, whereinthe step of irradiating the dielectric layer is at a partial pressure ofabout 10⁻² to about 10⁻⁷ Torr.
 31. The method of claim 29, wherein thesilicon-containing species is selected from the group consisting ofdichlorosilane, silicon tetrachloride, silane, and disilane.
 32. Themethod of claim 28, wherein the step of irradiating the dielectric layerwith the silicon-containing species is by plasma enhanced chemical vapordeposition, low pressure chemical vapor deposition, or rapid thermalchemical vapor deposition.
 33. The method of claim 28, wherein the stepof irradiating the dielectric layer with the silicon-containing speciesis by rapid thermal chemical vapor deposition at a temperature of about500° C. to about 700° C.
 34. The method of claim 28, wherein thedielectric layer comprises silicon dioxide.
 35. The method of claim 28,wherein the dielectric layer comprises a dielectric material selectedfrom the group consisting of tantalum pentoxide, hafnium dioxide, andaluminum trioxide.
 36. A method of forming a semiconductor device,comprising the steps of: exposing a dielectric layer disposed on asilicon substrate to a silicon-containing species at a partial pressureof about 1 Torr or less to nucleate the dielectric layer with a layer ofsilicon; and nitridizing the silicon layer in a nitrogen-containingspecies.
 37. A method of forming a semiconductor device, comprising thesteps of: exposing an oxide layer disposed on a silicon substrate to asilicon-containing species at a partial pressure of about 10⁻² Torr orless to nucleate the dielectric layer with a layer of silicon; andthermally annealing the silicon layer in a nitrogen-containing gas. 38.A method of forming a semiconductor device, comprising the steps of:exposing an oxide layer disposed on a silicon substrate to asilicon-containing species at a partial pressure of about 10⁻² Torr orless to nucleate the dielectric layer with a layer of silicon; andexposing the silicon layer to a nitrogen-containing species at atemperature of about 700° C. to about 900° C. to nitridize the siliconlayer.
 39. A method of forming a semiconductor device, comprising thesteps of: depositing a silicon layer onto a dielectric layer by exposingthe dielectric layer to a silicon-containing species under low partialpressure to nucleate the dielectric layer with a layer of silicon; andexposing the silicon layer to a plasma source of a nitrogen-containingspecies to nitridize the silicon layer.
 40. The method of claim 39,wherein the plasma source of the nitrogen-containing species is producedby a downstream microwave system, an electron cyclotron residencesystem, an inductive coupled plasma system, or a radio frequency system.41. A method of forming a semiconductor device, comprising the steps of:depositing a silicon layer onto a dielectric layer by exposing thedielectric layer to a silicon-containing species under low a partialpressure of about 1 Torr or less to nucleate the dielectric layer with alayer of silicon; and exposing the silicon layer to a remote microwaveplasma source of a nitrogen-containing species at a pressure of about 1to about 20 Torr to nitridize the silicon layer.
 42. A method of forminga gate electrode, comprising the steps of: exposing a gate oxide layerdisposed on a silicon substrate to a silicon-containing species at apartial pressure of about 10⁻² Torr or less to nucleate the dielectriclayer with a layer silicon; and exposing the silicon layer to anitrogen-containing species to form a silicon nitride barrier layer. 43.A method of forming a gate electrode, comprising the steps of: exposinga gate oxide layer disposed on a silicon substrate to asilicon-containing species at a partial pressure of about 10⁻² to about10⁻⁷ to nucleate the dielectric layer with a layer of silicon; andexposing the silicon layer to a nitrogen-containing species to form asilicon nitride barrier layer.
 44. A method of forming a gate electrode,comprising the steps of: exposing a gate oxide layer disposed on asilicon substrate to a silicon-containing species at a partial pressureof about 10⁻² to about 10⁻⁷, a temperature of about 500° C. to about700° C., and a duration of about 1 second to about 5 minutes, tonucleate the dielectric layer with a layer of silicon and exposing thesilicon layer to a nitrogen-containing species to form a silicon nitridebarrier layer.
 45. A method of forming a gate electrode, comprising thesteps of: depositing a silicon layer onto a gate oxide layer disposed ona silicon substrate by exposing the gate oxide layer to asilicon-containing species at a partial pressure of about 10⁻² Torr orless; and thermally annealing the silicon layer in a nitrogen-containingspecies.
 46. A method of forming a gate electrode, comprising the stepsof: depositing a silicon layer onto a gate oxide layer disposed on asilicon substrate by exposing the gate oxide layer to asilicon-containing species at a partial pressure of about 10⁻² Torr orless; and exposing the silicon layer to a nitrogen-containing species ata temperature of about 700° C. to about 900° C. to nitridize the siliconlayer to a silicon nitride layer.
 47. A method of forming a gateelectrode, comprising the steps of: depositing a silicon layer onto agate oxide layer disposed on a silicon substrate by exposing thedielectric layer to a silicon-containing species under low partialpressure; and exposing the silicon layer to a nitrogen-containingspecies at a temperature of about 700° C. to about 900° C., a pressureof about 1 to about 760 Torr, a flow rate of about 100 to about 10,000sccm, for about 1 second to about 180 minutes to nitridize the siliconlayer.
 48. The method of claim 47, wherein the nitrogen-containingspecies is selected from the group consisting of nitrogen, ammonia,nitrogen trifluoride, nitrogen oxide, and a mixture of nitrogen andhelium.
 49. A method of forming a gate electrode, comprising the stepsof: depositing a silicon layer onto a gate oxide layer disposed on asilicon substrate by exposing the dielectric layer to asilicon-containing species at a partial pressure of about 10⁻² Torr orless; and exposing the silicon layer to a plasma source of anitrogen-containing species to nitridize the silicon layer.
 50. Themethod of claim 49, wherein the plasma source of the nitrogen-containingspecies is produced by a downstream microwave system, an electroncyclotron residence system, an inductive coupled plasma system, or aradio frequency system.
 51. A method of forming a gate electrode,comprising the steps of: depositing a silicon layer onto a gate oxidelayer disposed on a silicon substrate by exposing the dielectric layerto a silicon-containing species at a partial pressure of about 10⁻² Torror less; and exposing the silicon layer to a remote microwave plasmasource of a nitrogen-containing species at a temperature of about 700°C. to about 900° C., and a pressure of about 1 to about 20 Torr tonitridize the silicon layer.
 52. A method of forming a gate electrode,comprising the steps of: depositing a silicon layer onto a gate oxidelayer disposed on a silicon substrate by exposing the dielectric layerto a silicon-containing species at a partial pressure of about 10⁻² Torror less; and exposing the silicon layer to an inductive coupled plasmasource of a nitrogen-containing species at a pressure of about 1 toabout 20 Torr to nitridize the silicon layer.
 53. A method of forming agate electrode, comprising the steps of: exposing a gate oxide layerdisposed on a silicon substrate to a silicon-containing species at apartial pressure of about 10⁻² to about 10⁻⁷ to nucleate the dielectriclayer with a layer of silicon; nitridizing the silicon layer in anitrogen-containing species to form a silicon nitride barrier layer; andforming a conductive polysilicon layer comprising a conductivityenhancing dopant over the nitride barrier layer; wherein the nitridebarrier layer inhibits passage of the dopant from the conductivepolysilicon layer therethrough.
 54. The method of claim 53, wherein thepolysilicon layer comprises a boron dopant.
 55. The method of claim 53,further comprising: forming an insulative nitride cap over theconductive polysilicon layer; and patterning the layers to form a gatestack.
 56. The method of claim 53, further comprising: forming a barrierlayer over the doped polysilicon layer; forming a conductive metal layerover the barrier layer; forming an insulative nitride cap over theconductive metal layer; and patterning the layers to form a gate stack.57. The method of claim 53, further comprising: forming a metal silicidelayer over the doped polysilicon layer; forming an insulative nitridecap over the metal silicide layer; and patterning the layers to form agate stack.
 58. A nitride barrier layer, comprising: a nitridizedsilicon layer of less than about 30 angstroms disposed on an oxidelayer, and formed by irradiation of the oxide layer with asilicon-containing species under low partial pressure in the presence ofa nitrogen-containing species.
 59. A nitride barrier layer, comprising:a nitridized silicon layer having a thickness of less than about 30angstroms, and disposed adjacent an oxide layer.
 60. A nitride barrierlayer, comprising: an annealed nitridized silicon layer having athickness of less than about 30 angstroms, and disposed adjacent anoxide layer.
 61. The barrier layer of claim 60, wherein the barrierlayer is thermally annealed.
 62. The barrier layer of claim 60, whereinthe barrier layer is plasma annealed.
 63. A semiconductor devicecomprising: a semiconductor substrate comprising silicon; an oxide layerdisposed adjacent to the semiconductor substrate; and a diffusionbarrier layer disposed adjacent the oxide layer; the diffusion barrierlayer having a thickness of less than about 30 angstroms, and comprisinga nitridized silicon layer formed by irradiation of an oxide layer witha silicon-containing species under low partial pressure in the presenceof a nitrogen-containing species,
 64. A semiconductor device comprising:a semiconductor substrate comprising silicon; an oxide layer disposedadjacent to the semiconductor substrate; and a diffusion barrier layerdisposed adjacent the oxide layer, and comprising nitridized siliconhaving a thickness of about 10 to about 20 angstroms.
 65. Asemiconductor device comprising: a semiconductor substrate comprisingsilicon; an oxide layer disposed adjacent to the semiconductorsubstrate; and a diffusion barrier layer disposed adjacent the oxidelayer, and comprising nitrogen annealed silicon and having a thicknessof about 10 to about 20 angstroms.
 66. The device of claim 65, whereinthe diffusion barrier layer comprises plasma annealed silicon.
 67. Thedevice of claim 65, wherein the diffusion barrier layer comprisesthermally annealed silicon.
 68. A gate electrode, comprising: a gateoxide layer disposed adjacent to a semiconductor substrate; and adiffusion barrier layer disposed adjacent the gate oxide layer; thediffusion barrier layer having a thickness of about 10 to about 20angstroms and comprising a nitridized silicon layer deposited byirradiating an oxide layer with a silicon-containing species under lowpartial pressure, and nitridizing the silicon layer by exposure to anitrogen-containing species.
 69. A gate electrode, comprising: a gateoxide layer disposed adjacent to a semiconductor substrate; and adiffusion barrier layer disposed adjacent the oxide layer, andcomprising a nitridized silicon layer having a thickness of about 10 toabout 20 angstroms.
 70. A gate electrode, comprising: a gate oxide layerdisposed adjacent to a semiconductor substrate; and a diffusion barrierlayer disposed adjacent the oxide layer, and comprising nitrogenannealed silicon and having a thickness of about 10 to about 20angstroms.
 71. The electrode of claim 70, wherein the diffusion barrierlayer comprises plasma annealed silicon.
 72. The electrode of claim 70,wherein the diffusion barrier layer comprises thermally annealedsilicon.